1. Field of the Invention
The invention relates to the field of safety technology for electric switchgear cabinets. The invention proceeds from a safety door-locking system according to the preamble of patent claim 1.
Safety door-locking systems of said type are known, for example, from the notification "Miniatur Sicherheitstutrschalter" ("miniature safety door switches") in the publication "Aktuelle Technik", No. 5/96, page 397 from B+L Verlags AG.
2. Discussion of Background
Safety door-locking systems for switchgear cabinets in electrical installations, as they are known from the prior art, serve the purpose of operating safely and protect the staff who operate and care for the electrical installations. An example of the simplest type of a safeguarded door lock is locking the switchgear cabinet doors by means of a multiplicity of screw-type systems which can be operated only with a special tool. A decisive disadvantage in such screwing systems is that they can be opened only with a large outlay on time by specialist staff with appropriate equipment, and this is very cumbersome in the case, for example, of a fault inside a switchgear cabinet. In addition, a simple screwing system cannot be coupled to an operating state inside a switchgear cabinet, with the result that it is necessary to set up a safeguarded electric switching state before the cabinet door is opened by the responsible specialist staff.
A locking device which is by far simpler to operate is known by the name of "Kirk Key" locking system. Such a system comprises in a mechanical locking unit at least two mutually coupled locking cylinders with different coding for the associated keys. This requires, for example, that before a switchgear cabinet is opened a first key must be used to set up a position for a grounding switch, whereupon the second key in the locking unit becomes freely operable, said second key thereupon being used to open a cabinet door. If a multiplicity of switchgear cabinets are mechanically locked in this way one after another in a row, opening the last cabinet in the row is also correspondingly time-consuming.
An example, of combined electromechanical locking is shown by the prior art in the notification "Miniatur Sicherheitsturschalter" ("miniature safety door switches") in the publication "Aktuelle Technik", No. 5/96, page 397 from B+L Verlags AG. Such a variant locking system essentially comprises a door switch which is mounted in the switchgear cabinet and cooperates with a coded key fastened to the cabinet door. In this arrangement, the door switch is electrically controlled, and the key is fixed or released mechanically in the door switch as a function of the control system. It is therefore possible in a simple way to lock or unlock in a controlled fashion a multiplicity of switchgear cabinets in parallel as a logical function of required positions of switches inside the switchgear cabinets. Certainly, the wider, but still limited range of operating temperature is a disadvantage of such locking systems. In addition, said system depends directly on the operational safety of the feeding electric network for the door switches and, moreover, on the operational safety of the connected control system. In addition, an installation of this type is correspondingly intensive in terms of cost and maintenance.